Benzotriazole, mercaptobenzothiazole and tolyltriazole are well known copper corrosion inhibitors. For example, see U.S. Pat. No. 4,675,158 and the references cited therein. This patent discloses the use of tolyltriazole/mercaptobenzothiazole compositions as copper corrosion inhibitors. Also, see U.S. Pat. No. 4,744,950, which discloses the use of lower (C.sub.3 -C.sub.6) alkylbenzotriazoles as corrosion inhibitors, and corresponding EPO application No. 85304467.5.
U.S. Pat. No. 4,338,209 discloses metal corrosion inhibitors which contain one or more of mercaptobenzothiazole, tolyltriazole and benzotriazole. Examples of formulations containing benzotriazole and tolyltriazole and formulations containing mercaptobenzothiazole and benzotriazole are given.
Copending patent application U.S. Ser. No. 348,521 relates to the use of higher alkylbenzotriazoles as copper and copper alloy corrosion inhibitors, copending patent application U.S. Ser. No. 348,532 relates to the use of alkoxybenzotriazoles as copper and copper alloy corrosion inhibitors, and copending patent application U.S. Ser. No. 540,977 relates to the use of alkylbenzotriazole/mercaptobenzothiazole, tolyltriazole, benzotriazole and/or phenyl mercaptotetrazole compositions as copper and copper alloy corrosion inhibitors.
U.S. Pat. No. 4,406,811 discloses compositions containing a triazole such as tolyltriazole, benzotriazole or mercaptobenzothiazole, an aliphatic mono- or di-carboxylic acid and a nonionic wetting agent.
U.S. Pat. No. 4,363,913 discloses a process for preparing 2-aminobenzothiazoles and alkyl and alkoxy-substituted aminobenzothiazoles.
U.S. Pat. No. 2,861,078 discloses a process for preparing alkyl and alkoxy-substituted benzotriazoles.
U S. Pat. No. 4,873,139 discloses the use of 1-phenyl-1H-tetrazole-5-thiol to prepare corrosion-resistant silver and copper surfaces. The use of 1-phenyl-5-mercaptotetrazole to inhibit the corrosion of carbon steel in nitric acid solutions is also known. See Chemical Abstract CA 95(6):47253 (1979).
U.S. Pat. No. 4,014,814 discloses corrosion inhibiting compositions comprising phenyl-aldehyde resins and polyphosphates.
The present invention relates to corrosion inhibiting compositions comprising a) a polyphosphate; and b) an azole, preferably a compound selected from the group consisting of C.sub.2 -C.sub.12 alkyl or alkoxy benzotriazoles, mercaptobenzothiazole, tolyltriazole, benzotriazole, substituted benzotriazoles such as chlorobenzotriazole, nitrobenzotriazole, etc. and 1-phenyl-5-mercaptotetrazole, and salts thereof and the use thereof as corrosion inhibitors, particularly copper and copper alloy corrosion inhibitors. In these compositions the polyphosphate component is believed to assist adsorption of the inhibitor component, thereby improving inhibition on the metal surface being treated. The instant compositions are especially effective in the treatment of copper and copper alloy surfaces, particularly copper/nickel alloy surfaces Additionally, these compositions generally provide improved tolerance to oxidizing biocides such as chlorine and bromine.
The use of the instant blends of a) polyphosphates and b) an azole, preferably at least one of C.sub.2 -C.sub.12 alkyl-or alkoxybenzotriazoles, tolyltriazole, benzotriazole and 1-phenyl-5-mercaptotetrazole or related compounds provides substantial corrosion inhibition, even in aggressive waters. It is theorized that the corrosion inhibition provided by azoles is due to the formation of a cuprous/azole complex. Cupric (Cu(II)) azoles are not believed to be protective, and can even be detrimental if their presence results in the formation of Cu(II) azole nodules on the surface of the metal being treated. Therefore, it is theorized, compounds which can remove or slow the formation of the cupric oxide corrosion film will assist the penetration of the azole to the cuprous oxide layer by preventing the undesirable buildup of the Cu(II) azole complex at the surface. It is believed, though the inventors do not wish to be bound by this mechanism, that the instant compositions help to reduce the undesirable deposition of cupric oxides on metallic surfaces, thereby allowing the azole better access to the cuprous oxide surface. Thus, the instant compositions provide effective film formation, provide chemically resistent corrosion protection and overcome problems relating to the failure to obtain passivation due to Cu(II) azole complexes, particularly in aggressive, high-solids waters.
As used herein the term "passivation" refers to the formation of a film which lowers the corrosion rate of the metallic surface which is being treated. "Passivation rate" refers to the time required to form a protective film on a metallic surface. Also, the term "high solids water" refers to water which contains dissolved solids in excess of about 1,500 mg/L. Dissolved solids include, but are not limited to, anions released from chlorides, sulfates, silicates, carbonates, bicarbonates and bromides; and cations such as lithium, sodium, potassium, calcium and magnesium.
The instant polyphosphate/azole compositions, or the use thereof for corrosion control, are not known or suggested in the art.